I was able to hold the PRMI on REFL33I&Q, and have ALS CARM and DARM at zero CARM offset. The arm would "buzz" through the resonance regularly. I use the word buzz because that's kind of what it sounded like. This is the noise of the ALS system.
Here is a plot of when the arm powers went pretty high from last night. CARM and DARM were on ALS comm and diff, PRMI was on REFL33 I&Q. I set the CARM offset so that I was getting some full arm resonances, and it goes back and forth over the resonance.
The Y axes aren't perfect when I zoom, but the maximum TRX value was 98 in this plot, while the max TRY value was 107.
MICH_OUT was hitting its digital rails sometimes, and also it looks like PRCL and MICH occasionally lost lock for very brief periods of time.
Glitch-like events in PRCL_OUT are at the edges of these mini-locklosses. I don't know why POPDC has glitch-y things, but we should see if that's real.
Okay, I've zoomed in a bit, and have found that, interestingly, I see that both POP22 and POP110 decrease, then increase, then decrease again as we pass through full resonance. This happens in enough places that I'm pretty sure we're not just going back and forth on one side of the resonance, but that we're actually passing through it. Q pointed out that maybe our demod phase angle is rotating, so I've made some zoom-in plots to see that that's not a significant effect. I plot the I and Q phases individually, as well as the total=sqrt(I**2 + Q**2), along with TRY (since the increases and decreases are common to both arms, as seen in the plot above).
For POP 22:
For POP 110:
I also plot the MICH and PRCL error signals along with TRY and POP22 total. You can see that both MICH and PRCL were triggered off about 0.1msec after POP22 total this it's first super low point. Then, as soon as POP22 becomes large enough, they're triggered back on, which happens about 1.5msec later. (The triggering was actually on POP22I, not POP22tot, but the shapes are the same, and I didn't want to overcrowd my plots).
I am not sure if we consistently lose sideband signal in the PRC more on one side of the CARM resonance than the other, but at least POP22 and POP110 are both lower on the farther side of this particular peak. I want to think about this more in relation to the simulations that we've done. One of the more recent things that I see from Q is from September: elog 10502, although this is looking specifically at the REFL signals at 3f, not the 2f circulating PRCL power as a function of CARM offset.